[mod] addition of various type hints / tbc

- pyright configuration [1]_
- stub files: types-lxml [2]_
- addition of various type hints
- enable use of new type system features on older Python versions [3]_
- ``.tool-versions`` - set python to lowest version we support (3.10.18) [4]_:
  Older versions typically lack some typing features found in newer Python
  versions.  Therefore, for local type checking (before commit), it is necessary
  to use the older Python interpreter.

.. [1] https://docs.basedpyright.com/v1.20.0/configuration/config-files/
.. [2] https://pypi.org/project/types-lxml/
.. [3] https://typing-extensions.readthedocs.io/en/latest/#
.. [4] https://mise.jdx.dev/configuration.html#tool-versions

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Format: reST

searx/extended_types.py

@@ -62,6 +62,8 @@ class SXNG_Request(flask.Request):
     """A list of :py:obj:`searx.results.Timing` of the engines, calculatid in
     and hold by :py:obj:`searx.results.ResultContainer.timings`."""
 
+    remote_addr: str
+
 
 #: A replacement for :py:obj:`flask.request` with type cast :py:`SXNG_Request`.
 sxng_request = typing.cast(SXNG_Request, flask.request)